Do not wrap result errors when returning them (#73)

This PR removes the wrapping of in-house created result errors with
`Result.FromError` (I did not know this was possible until today, lol),
which reduces code verbosity and makes it easier to read, and replaces
`ArgumentNullError` with `ArgumentInvalidError` when retrieving IDs from
a command context, which, in my opinion, is more correct.

---------

Signed-off-by: Octol1ttle <l1ttleofficial@outlook.com>

src/Data/Options/LanguageOption.cs

@@ -29,6 +29,6 @@ public class LanguageOption : Option<CultureInfo> {
     public override Result Set(JsonNode settings, string from) {
         return CultureInfoCache.ContainsKey(from.ToLowerInvariant())
             ? base.Set(settings, from.ToLowerInvariant())
-            : Result.FromError(new ArgumentInvalidError(nameof(from), Messages.LanguageNotSupported));
+            : new ArgumentInvalidError(nameof(from), Messages.LanguageNotSupported);
     }
 }